The invention is concerned with a coupling for pipe of the type that is used in the hydraulic dredging industry and particularly with pipe that is used as dredge shore pipe and pontoon pipe.
The provision of adequate tension, compression and torsion strength in couplings of the steel pipe used for pontoon pipe and dredge shore pipe is important because of the high stresses applied to couplings of this type of pipe in normal use. For example, pontoon pipe which extends from the floating dredge to the shore or a spoil barge is subjected continuously to forces of wind and current, and to the forces which are applied when the pontoon pipe is moved under tow when it is being relocated. Flexibility in pontoon pipe lines is presently obtained through the use of ball joints or rubber sleeves between pipe lengths. Ball joints are in common use today but have the real disadvantage of extremely poor hydraulic characteristics. Slurry flow in a pipe travels at a certain speed or velocity. Since the inside of the ball necessarily has a larger cross-sectional area than the pipe, the velocity of flow is suddenly reduced when slurry enters the ball. When the slurry leaves the ball, it passes through the ball exit which is the diameter of the pipe. Upon leaving the ball, the slurry enters the bell when it experiences a second expansion and drop in velocity. Upon leaving the bell, the slurry enters the pipe, which has a smaller inside diameter than that of the bell. The result is that a ball joint is a consumer of power. A purpose of my invention is to reduce this consumption of power by using a smooth bore, flexible pontoon pipe connection. The ball joint is competent in tension. The use of rubber sleeves to provide flexibility between pontoon pipes is not extensive because rubber sleeves cannot withstand tension nor can they withstand bending. My pontoon pipe provides both flexibility and resistance to separation due to tensile forces.
The shore pipe which leads from the pontoon pipe to the spoil area is often laid over rugged ground and therefore may extend up and down hills. Movement in the couplings of shore pipe results in leakage and can even culminate in separation of the pipe. Further, the couplings of such pipe are stressed by the pulsations of the slurries of dredged material that are forced through the pipe by the hydraulic pump of the dredge.
Previous couplings for shore dredging pipe have been concerned with the prevention of leakage but have not attempted to form a coupling that would prevent separation of the pipe caused by the large tension and torsion forces that are experienced during dredging operations. The couplings that have provided a mechanical connection between shore pipes have not been sufficiently strong to resist the forces normally encountered in dredge pipeline operations. As a result, auxiliary tension resisting devices such as strapping have been used between the couplings of shore pipe to resist separation.
An object of this invention is a bell and spigot connection for pipe such as dredging pipe that provides a smooth bore, self-alignment of connecting pipes and a minimum, if any, gap between the pipes to reduce turbulence and friction loss.
Another object of this invention is a bell and spigot connection for hydraulic dredging pipe which provides a strong physical connection against separation and breakage due to tension, compression and torsion forces, i.e., a physical connection that is almost as strong as that of the pipe itself.
Another object of this invention is a bell and spigot connection for hydraulic pipe in which the packing is trapped between metal-to-metal portions of the bell and spigot ends of the pipes.
Another object of this invention is a bell and spigot connection having an outer metal-to-metal contact between the bell and a stepped ring on the spigot to absorb the axial loading for compression and tension forces, an intermediate sleeve to define a packing gland with the toe of the stepped ring and an inner sleeve to align with the spigot of the pipe to eliminate any gap which would cause turbulence.
Another object of this invention is a bell and spigot connection for pipes that can be assembled by welding together easily formed parts and which does not require any elaborate castings or machined parts for the connection.
Another object of this invention is a rubber sleeve, flexible pontoon pipe connection which replaces the conventional machined ball joint for connecting pontoon pipes.
Other objects ma be found in the following specification, claims and drawings.